Neonatal Hyperbilirubinemia is due to which condition?

• A. Transient UDPGT deficiency corrected after a week
• B. Permanent UDPGT deficiency
• C. Impaired bilirubin excretion only
• D. Normal bilirubin metabolism

Answer: (A)

Neonatal unconjugated hyperbilirubinemia occurs because the liver’s ability to conjugate bilirubin is immature at birth. The key enzyme, UDP-glucuronosyltransferase, has very low activity in newborns and then increases over the first days to weeks. This transient deficiency means bilirubin stays in its unconjugated form until conjugation ramps up, producing the common, self-limited jaundice of the newborn. As the enzyme activity matures, bilirubin is conjugated and excreted, and the jaundice resolves—typically within about a week or so in term infants. If the deficiency were permanent, as in Crigler-Najjar, the high unconjugated bilirubin would persist. If bilirubin excretion were impaired alone, you’d expect a different pattern, usually involving conjugated bilirubin elevation from cholestasis. Normal bilirubin metabolism would not produce hyperbilirubinemia.